Exam 3: Anaerobic Infections Flashcards
What are the major anaerobic pathogens?
GP spore forming rods (clostridium)
GP non-sporeforming rods (actinomyces, propionbacterium, eubacterium)
GN rods (bacteroides and fusobacterium)
GP cocci (peptococcus and peptostreptococcus)
What is the body’s normal flora and mucosal surfaces like?
Normal flora: predominately anaerobic
Mucosal surfaces: heavily colonized by obligate anaerobes
Describe the bacteria in the fecal matter of the colon
Makes up 90% of fecal matter
Obligate anaerobes outnumber facultative anaerobes by more than 1000:1
Describe the ratio of obligate and facultative anaerobes to other bacteria in the mouth
They outnumber other bacteria by more than 10:1
Why can obligate anaerobes survive in the mouth in the presence of oxygen?
Because oral/viridans streptococci lower the red-ox potential
What do pathogenic strains of bacteroides and fusobacterium produce as a virulence factor?
Polysaccharide capsules (antiphagocytic) Bacteroides also produce pili (adherence)
What often contributes to the adherence and cell toxicity of GN anaerobes?
Outer membrane proteins, LPS-endotoxin, and other cell surface components
What are common virulence factors?
Extracellular or cell-bound enzymes and leukocidins ir cytolysins
What is a virulence factor associated with intracellular activity?
Protein exotoxins
What enhances survival and virulence?
Synergistic mechanisms
What does Bacteroides spp. require for survival and virulence? Where does it get it?
Vitamin K
Gets it from nonpathogenic streptococci or other anaerobes
What does B. asacharolyticus do for survival and virulence?
Causes severe spreading of lesions supplied with succinate from klebsiella and other helper bacteria
How do facultative anaerobes provide a more favorable environment? What do anaerobes do with this?
By removing oxygen and adding reducing substances as the infection matures
Anaerobes return the favor by producing leukotoxins and depleting opsonins and complement
What clinical feature is consistently associated with obligate anaerobes?
A putrid odor
List the remaining clinical features for anaerobic infections
Clostridial myonecrosis Oropharyngeal and cutaneous infections Pleuropulmonary infections Intra-abdominal infections Osteomyelitis Reproductive tract infections *Read these
What are the staining characteristic of bacteroides?
GN rods
Very pleomorphic and may be beaded, coccoid, or slender
Often stain poorly and are difficult to see
Sometimes bipolar staining
What are the staining characteristic of clostridium?
GP rods
Large, chains
Spores swell the sporangium greatly
What are the staining characteristic of fusobacterium?
GN rods
Thin, pale, with tapered or pointed ends and a cigar or needle shape
What are the staining characteristic of actinomyces?
GP rods (or gram variable) Small, thin May form branched filaments or tangled mats May be beaded and poorly visible May form sulfur granules
What are the staining characteristic of peptococcus and peptostreptococcus?
GP cocci
Small, singly, pairs, or clusters in pairs and chains
Smaller, but cannot be distinguished from aerobic cocci
What are examples of acceptable collection and transport of specimens for culture?
Aspirates from enclosed lesions or body sites normally sterile
TTA or lung aspirates
Uterine aspirates
Aspirates of abscesses, deep wound
Tissue obtained from deep infections during debridement
Sequestra, bone biopsies, or nearby soft tissue
Blood
Aspirates from occeous bullae or frontal sinus
What are examples of unacceptable collection and transport of specimens for culture?
Swabs of pus from superficial wounds or draining tracts Urine Mouth, pharynx, or upper airway swabs Swabs from vagina. cervix, urethra Feces Saliva or nasal exudates Ear swabs Cerebrospinal fluid, nasotracheal and bronchoscopic aspirates
What are the most efficacious antibiotics for anaerobes?
Penicillins
Chloramphenicol
Clindamycin
Metronidazole
Which antibiotics are not the most efficacious to treat anaerobes but are often given concurrently to cover GN enterics?
Aminoglycosides
